The present invention relates generally to an apparatus with a vacuum system, such as an electron-beam exposure apparatus, an electron microscope or the like, in which apparatus the vacuum system includes a vacuum chamber adopted to contain main instruments of the apparatus, and the exhaust device adapted to exhaust air from the vacuum chamber, and more particularly to a structure for vibration isolation adapted to prevent the transmission of the vibration of the exhaust device to the main section of the apparatus, which structure is particularly adopted for the apparatus in which the exhaust device comprises a cryopump adopted as an air exhausting pump.
In recent years, as one type of vacuum pump, the cryopump was developed, which is small in size and light in weight and also is excellent in both the air exhausting rate and the attainable degree of the vacuum, and which has been very often adopted as the air exhausting pump for an apparatus with a vacuum system. In the cryopump, however, the generation of a low frequency vibration of about 2-3 [Hz] is unavoidable, due to the construction of the pump. Meanwhile, among various apparatuses with vacuum systems in which the exhaust devices comprise cryopumps, there are some apparatuses which are extremely adversely affected by the vibration, such as an electron-beam exposure apparatus, an electron microscope, or the like. Accordingly, methods have been devised to provide such an apparatus with a system for vibration isolation which utilizes air, rubber, springs or the like. However, such systems for vibration isolation provide for the elimination of vibrations having frequencies of more than several tens [Hz], but do not eliminate low frequency vibrations of 2-3 [Hz].
For the purpose of providing the elimination of such low frequency vibrations, a structure for vibration isolation is proposed, in which the vacuum chamber is connected via a bellows with the cryopump, which is secured to a fixed base, whereby the vibration of the cryopump is absorbed by the bellows. In accordance with this structure, the vibration of the cryopump is absorbed to a relatively great extent. However, this structure requires a bellows having a long length, which is very expensive, costing as much as, or more than, the cryopump.